Fluid spring



l. D. SMITH 2,643,112

FLUID SPRING 2 Sheets-Sheet 1 June 23, 1953 Filed Dec. 25, 1948 INVENTOR.

IRA 0. SMITH l. D. SMITH FLUID SPRING June 23, 1953 2 Sheets-Sheet 2 Filed Dec. 23, 1948 mm mm H 5W M 0 Patented June 23, 1953 FLUID SPRING Ira D. Smith, Cleveland, Ohio, assignor to The Cleveland Pneumatic Tool Company,

Ohio, a corporation Cleveland,

Application December 23, 1948, Serial No. 66,985 (01. zen-s4) 4 Claims.

This invention relates broadly to shock absorbers, but more particularly to a fluid spring.

One object of this invention is to produce a fluid spring with simple and eflicient means affording a constant supply of liquid to the working cylinder, thereby preventing any void from occurring in the working cylinder and guaranteeing efiicient and constant operation of the spring.

Another object of this invention is to provide such a spring with a single cylinder having a pressure or working chamber within which the spring piston operates and a fluid reservoir from which fluid under pressure is automatically supplied to the working chamber in the event any void occurs therein through leakage or temperature changes.

Another object of this invention is to produce such a spring as a single unit, wherein the parts are readily accessible and forming an assembly of simple and efficient construction.

Other objects and advantages more or less ancillary to the foregoing reside in the specific construction and aggroupment oi the elements peculiar to this structure, as will become apparent from a more complete examination of this specification.

In the drawings which illustrate a preferred embodiment of the invention:

Figure 1 is a longitudinal sectional view of the spring shown in retracted or compressed position.

Figure 2 is an enlarged view of the central portion of the spring shown in Figure 1.

Figure 3 is a view similar to Figure 1 but showing the spring in extended position.

Figure 4 is an enlarged cross sectional view taken through the line |-l in Figure l and looking in the direction of the arrows.

Referring to the drawings, in which like symbols designate corresponding parts throughout the several views, ll! represents a cylinder or housing having its left end, as seen in Figures 1 and 3, provided with an eyed terminal H through which that end of the spring may be secured in operative position.

Internally, the housing In is accurately machined to produce two coaxially disposed cylindrical chambers t2 and I3, the what larger than the former and forming at their junction an annular step or shoulder H. The chamber l2, which is hereinafter referred to as the work chamber, is. normally closed at one end,

but capable of communication with the exterior of the housing In through a bleed port i5 which opens into a threaded bore l6 normally closed by a plug l'l.

latter being some The chambers 12 and [3 are separated by a partition assembly, generally designated by Hi, which includes a metal ring til resting against the annular shoulder l4 and held in that position by a split ring 20 partly located in an annular groove 2! formed in the wall of the chamber l3. A bore 22 extends centrally through the ring l9, and toward the chamber [2, the bore is enlarged to form a counterbore 23 accommodating a V-shaped block packing 24. The end face of the ring l9 adjacent the chamber I2 is provided with a large but shallow recess 25 having rigidly mounted therein a plate 26 through which the packing,

24 is held in position. This plate is also provided with a relativel large central bore 21 and a small port 23, which port is normally closed by a valve 29 slidably mounted in passage 38 which extends through the ring Hi. The passage 30 is somewhat larger than the valve '29 and is shaped to accommodate a compression spring 3i which acts on the head of the valve 29 for urging it in fluid tight engagement with the adjacent edge of the port 28. To assure a fluid tight joint between the ring I9 and the inner wall of the chamber l3, the former has its peripheral wall provided with an annular recess 32 accommodating an annular packing 33.

The right end of the chamber 13, as seen in Figures 1 and 3, is somewhat enlarged and threaded to receive a plug 34. having a central bore 35 extending therethrough and of a diameter larger than the bore 22 to accommodate a pressed in bushing 36.

Reciprocally mounted in the chamber I3, there is a floating piston or bulkhead assembly, generally designated by 31, which includes a metal ring 54 having a central bore 38 extending therethrough. Intermediate its ends. the bore 38 is provided with an internal annular recess 39 accommodating an annual packing 49. To assure a fluid tight but slidable fit between the floating piston and the inner wall of the chamber 13, the ring '54 has its peripheral wall provided with an annual recess 4| accommodating an annular packing 4'2. vToward the partition IS, the outside diameter of thering 54 is reduced as at 43. The adjacent end walls of the plug 34 and ring 54 are dug out to accommodate a compression spring 44, which has one end resting against the plug 34 and'the other end against the floating piston 31..

Reciprocally mounted in the work chamber l2, there is a'pist0n45, having a threaded bore 46, extending centrally therethrough and adapted to receive the threaded shank 41 of a piston rod 48. The piston is locked on the shank 41 by a set screw 49, and has a plurality of ports 58 extending longitudinally therethrough. From the piston 45, the rod 48 extends through the partition bore 22 and packing 24, floating piston bore 33 and packing 40, and the bushing 36 to end outside of the plug 34 where it is formed with an eye or terminal 5|.

A threaded hole 52 extends through the wall of the housing I and opens into the chamber I3 at a place adjacent to the partition I8. The hole 52 is adapted to receive a self-sealing hydraulic plug or fitting 53.

Preparatory to the operation of the device, the chamber .13, hereinafter referred to as reservoir, between the floating piston 31 and partition I3, is filled with liquid such as oil, admitted therein under pressure through the self-sealing fitting 53. Before liquid under pressure is introduced into the chamber I3, the floating piston 31 which includes the ring 54, acted upon by the spring 44, will rest against the spring split ring 20. In this position of the floating piston, the reduced portion 43 of the ring 513 is located under the fitting 53, thereby enabling the liquid under pressure to shift and maintain the floating piston in the position shown in Figures 1 and 3.

In practice, the size of the partition bore 22 is made to afford a rather loose sliding bearing for the piston rod 48, and enable pressure fluid to flow therethrough from the reservoir I3 into the chamber I2 by depressing the inner lip of the V-shaped packing 24 away from the piston rod 48. While filling the chamber I2, it is preferable to have the spring fully extended as'shown in Figure 3, so that the volumetric capacity of the chamber will not be reduced by any portion of the piston rod. In the chamber I2, the fluid will flow on both sides of the piston 45 through the piston ports 59. In order to prevent any air from being trapped in the chamber I 2, the plug I1 is removed and air allowed to escape through the bleed port I5. When both chamber I2 and reservoir I3 are completely filled with liquid, the plug I1 is screwed back in position to close the bleed port I5 and the device is ready for operation after the end terminals I I and SI have been connected to the work intended to be cushioned.

After both chamber I2 and reservoir I3 have been completely filled with liquid and before any load is applied on the end terminals of the spring, it will be understood that the pressure within the spring is substantially zero, or equal only to the pressure resulting from the compression spring 44. After being connected to the work intended to be cushioned, the end terminals of the spring will be subjected to a load which will cause a partial compression of the spring, which, together with the entering of the piston rod 48 into the chamber I2, will cause the liquid in that chamber to compress and the housing III to expand slightly and produce together a spring re sistance. The liquid thus compressed within the chamber I2 would in practice be diflicult to be retained in that chamber, and irrespective of the type and number of packing used in an'effort to prevent leakage, the liquid under pressure would sooner or later escape from that chamber. Furthermore, since the liquid used has a much higher coefficient of expansion than the housing I0, changes in temperature would also cause the spring either to build up a premature pressure in the chamber I2 or develop a void therein depending on whether the temperature is increased or decreased. Obviously, leakage of liquid from the chamber I2 or a variation of its pressure therein resulting from changes in temperature, would immediately affect the eflicient operation of the spring and cause it to lose its original design characteristics. Moreover, should the spring besubjected to an accidental load above the maximum for which it is designed, it would subject t hhe liquid in the chamber I2 to an excessive pressure which might cause distortion of the spring and even breakage of the cylinder II).

In the present construction, should leakage of the liquid take place from the chamber I2 past the packing 33, or a void be created in the chamber I2 such as might result from a drop in temperature, the liquid stored in the reservoir I3 and acted upon by the spring pressed floating piston 31, will, when the unit is returned to its extended length as shown in Figure 3, be forced back into the chamber I2 by flowing between the piston rod 48 and partition bore 22, and by depressing the inner lip of the packing 24 away from the piston rod. In other words, the liquid stored in the reservoir I3 and under constant pressure through the action of the spring pressed floating piston 31, serves as a medium to automatically replenish the chamber I2, thereby assuring the working chamber I2 to be always completely filled with liquid and consequently constant eflicient operation of the spring.

To prevent the liquid in the chamber I2 from being subjected to excessive pressure, in the event of an extreme temperature raise, there is provided the safety valve 29, which valve is normally closed by the compression spring 3|. In practice, the spring 3| is calculated to compress when the pressure of the liquid in the chamber I2 reaches a predetermined maximum. In this instance, the liquid under pressure will act on the valve to shift it away from its seat and enable the liquid under excessive pressure to flow through the port 28 into the reservoir I3. As soon as the excessive pressure has been released, the valve 29 through the action of its spring 3!, will be returned to its seat to close the port 28. The void thus created in the chamber I2 when the temperature returns to normal will automatically be replenished by liquid returned into the chamber I2 from the reservoir I3 in the manner above stated.

During long and continuous operation of the spring, the liquid stored in the reservoir I3 might gradually leak past the packing 42. This leakage would not affect the working characteristics of the spring as long as a sufhcient amount of liquid remains in the reservoir I3 between the partition I8 and the floating piston 31. Should, however, the leakage of the fluid past the packing 42 become excessive, it would be necessary to drain the liquid from the right side of the floating piston as seen in Figures 1 and 3 by removing the plug 34 and subsequently refilling the reservoir I3 through the fitting 53.

From the foregoing description, it will be un-.

derstood that the present liquid spring is equipped with a self contained device assuring the spring to be always completely filled with liquid, thereby preventing the formation of void in the spring chamber which would materially aflect the emciency of the spring. It will also be understood that the present spring is equipped with a self contained safety device, which includes the valve 29, preventing excessive pressure to be created within the spring working chamber.

Also the foregoin description is necessarily of a detailed character, in order to completely set forth the invention, it is to be understood that the specific terminology is not intended to be restrictive or confining and it is to be further understood that various rearrangements of parts and modifications of structural detail may be resorted to without departing from the scope or spirit of the invention as herein claimed.

I claim:

1; A fluid spring including a housing, a work chamber and a reservoir in said housing filled with liquid, a partition between said chamber and reservoir, a piston slidable in said chamber having a. piston rod extending therefrom through said partition, reservoir and one end of said housing, end terminals on said housing and piston rod adapted to be secured to the work intended to be cushioned, a floating piston slidable in said reservoir on said piston rod, means operatively associated with said floating piston for causing it to exert pressure on the liquid stored in said reservoir, and means in said partition automatically supplying liquid under pressure from said reservoir to said chamber.

2. A fluid spring including a housing, a work chamber and a reservoir in said housing filled with liquid, a partition between said chamber and reservoir, a piston slidable in said chamber having a piston rod extending therefrom through said partition, reservoir and one end of said housing, end terminals on said housing and piston rod adapted to be secured to the work intended to be cushioned, said piston having its movement in said chamber retarded by the liquid stored therein while exerting pressure thereon, means in said partition enabling liquid in said chamber when subjected to a predetermined pressure to automatically be released into said reservoir, and means including a spring pressed floating piston slidable in said reservoir independently of the piston in said chamber for automatically returning liquid to said chamber when the liquid therein falls below said predetermined pressure.

3. A fluid spring including a housing, a work chamber and a reservoir in said housing filled with liquid, a partition between said chamber and reservoir, a piston slidable in said chamber having a piston rod extendingtherefrom through said partition, reservoir and one end of said housing, end terminals on said housing and piston rod adapted to be secured to the work intended to be cushioned, said piston having its movement in said chamber retarded by the liquid stored therein while exerting pressure thereon, a port through said partition leading from said chamber to said reservoir, a valve normally closing said port, said valve being subjected to the pressure of the liquid in said chamber and automatically opened thereby relative to said port when said pressure reaches a predetermined maximum to enable release of the liquid from said chamber to said reservoir, a spring acting on said valve automatically closing it relative to said port when said pressure falls below said maximum, and means including a spring pressed floating piston slidable in said reservoir independently of the piston in said chamber for automatically returning the liquid from said reservoir to said chamher.

4. A fluid spring including a housing, a work chamber in said housing filled with liquid, a piston slidable in said chamber having a piston rod extending therefrom through one end of said housing, end terminals on said housing and piston rod adapted to be secured to the work intended to be cushioned, a liquid reservoir, a floating element slidable in said reservoir, said piston rod extending through said reservoir and'floating element, means operatively associated with said floating element causing it to exert pressure on the liquid stored in the reservoir, said chamber from both sides of said piston being normally closed from said reservoir, and means leading from said reservoir to said chamber automatically opened during certain conditions of operation for supplying liquid under pressure from said reservoir to said chamber.

IRA D. SMITH.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,768,696 Laddon July 1, 1930 1,886,712 Messier Nov. 8, 1932 2,342,381 Thornhill Feb, 22, 1944 2,346,667 Dowty Apr. 18, 1944 2,564,790 Orloff et a1. Aug. 21, 1951 

